1. Field of the Invention
The present invention relates to an inductive load driving device.
Priority is claimed on Japanese Patent Application No. 2010-213096, filed Sep. 24, 2010, the content of which is incorporated herein by reference.
2. Description of the Related Art
Japanese Patent Laid-Open Publication No. 2008-85046 discloses an inductive load driving device including: a first switching element coupled between one end of an inductive load and an external power supply; a second switching element coupled between the other end of the inductive load and a ground terminal; a looping circuit configured to supply to the ground terminal, a counter current output from the inductive load when the first switching element is in off-state and the second switching element is in on-state; a counter current regeneration circuit configured to supply to the external power supply, a counter current output from the inductive load when the first and second switching elements are in off-state.
The inductive load driving device having the above configuration controls a ratio between durations of the on-state and the off-state of the first switching element (i.e., duty cycle), and thereby can control the rise characteristics. Additionally, the inductive load driving device controls the duty cycle of the second switching element while keeping the first switching element in off-state, and thereby can supply a counter current output from the inductive load to the external power source while controlling the fall characteristics.
Regarding the above inductive load driving device, when a power is supplied from a power circuit, such as a booster circuit, a counter current, which is output from the inductive load when the first and second switching elements are in off-state, flows to the output terminal of the power circuit through the counter current regeneration circuit. Generally, the power circuit includes a capacitor coupled between the output terminal of the power circuit and the ground terminal. When the counter current flows to the output terminal of the power circuit, a voltage, which is obtained by subtracting the amount of voltage drop caused by the counter current regeneration circuit from the counter voltage, is applied to the capacitor. When the applied voltage exceeds the rated voltage, the capacitor might be broken down.